1. Field of the Invention
The present invention relates to input devices for computer systems and more particularly to input devices indicating position or motion.
2. Description of Prior Art
With the growing computerization of society, the need for a wide variety of input devices has increased. In the past, data and information from the operator has been provided to computer systems through a variety of operator terminal devices such as keypunched card readers and tape readers. More recently interactive alphanumeric keyboards have become the standard means for operators to communicate with computer systems. While the alphanumeric keyboard was adequate for entering textual data, it was of very limited use for moving a point or cursor on a display screen or otherwise represented by the computer in any spatial direction or orientation. To overcome these inherent limitations on keyboard entry devices, a number of graphical input devices such as are known in the industry as "joysticks", "tracker balls" and more recently the "mouse" were developed to permit the entry of spatial orientation data or desired graphical information into a computer. A number of these devices were explained in W. Neuman and R. Sproull, Principles of Interactive Computer Graphics, McGraw Hill Co., pp. 147-157 (1979).
As explained in the Neuman and Sproull article, the mouse was rested on a flat surface and moved in the plane defined by the supporting surface as desired. Rotation of wheels located on the bottom of the mouse was interpreted by encoding devices mounted on orthogonal shafts to determine the relative movement of the mouse along each of the orthogonal axes. This movement information was transmitted to the computer for processing. The mouse therefore provided data corresponding to two-dimensional, orthogonal movement, but was limited by the requirement that it be located on a flat surface and could not provide three dimensional movement data such as that corresponding to rotation about a central axis.
U.S. Pat. No. 4,578,674 disclosed a wireless cursor positioning control device which used infrared and ultrasonic signals to determine the direction of motion in the orthogonal directions of the positioning device. The reference indicated without specific details that three dimensional control could be developed using the techniques disclosed. Even assuming a three dimensional control system was developed using these infrared and ultrasonic techniques, any such system would have been limited by the requirement of an unblocked line-of-sight transmission between the positioning device and the control base for transmission of the infrared and ultrasonic signals. This greatly limited the feasibility of infrared and ultrasonic systems for use in a 3-dimensional rotational situation and in a number of other 3-dimensional translational situations.
The Neuman and Sproull reference discussed tablet devices which were useful in digitizing material for input into a computer system. In tablet devices a digitizing surface was used in conjunction with a cross hair or cursor which could be moved to a desired position on the tablet surface. A switch was mounted to enable the operator to input data corresponding to the instantaneous position of the cross hair device on the tablet as a key point for use by the computer. These digitizing tablets worked on acoustic or magnetic properties and were limited to 2-dimensional operation. A 3-dimensional version was described in the Neuman and Sproull reference which used three acoustic microphone systems located on the tablet and one speaker system located in a pen. The system was limited to indicating only translational position and not the various rotational positions of the input device. A variant on this device used ultrasonic transmitters placed around the table and a microphone located in a pen. This variation had the same rotational limitations.
Mechanical devices were also used to indicate 3-dimensional locations wherein reels mounted at a fixed location were moved to the desired point and the relative motion was computed. These devices had the disadvantage that they were limited to translation values and could not provide rotational indications of the body.
U.S. Pat. No. 4,601,206 showed an inertial platform accelerometer cluster used to develop acceleration signals for directional and angular accelerations about the orthogonal axes.
U.S. Pat. No. 3,597,598 disclosed an accelerometer system employing three accelerometers and three angular error sensors to provide acceleration signals indicative of an alternate coordinate system.